the agency, function, or office of a deputy who acts as a substitute for another.

authority, power to act for another

a person authorized to work for another

In computer term, there is no exact description what is proxy. To make it easy to understand, I may say proxy is as an application that acts as a substitute for another applications. At the first time, proxy was designed to create cache files every time we surf on the internet because at the beginning, internet access was not as fast as what we have now. So, if we use cache files, next time we visit the same website, computer doesn’t have to download all the contents again because it’s already saved in the cache files which it will increase the downloading speed.

Now internet connection is getting faster, faster and faster. We still need cache program but not as much as before. Proxy still do its job but it has an additional job, firewall. With proxy, Network Administrator can block Ports, Internet Link and even set bandwidth quota.